[tsp-client] Fix error reported when the typespec project dir doesnt exist in cloned repo

[catalinaperalta]

Fixes #13413

This happens when there is a valid commit, but that commit doesn't contain the typespec project, so the entire sparse checkout process including the commit checkout pass, but when tsp-client attempts to look for the typespec project directory it doesnt exist for that specific commit. Users would have to verify that they configured the right project directory and commit in tsp-location.yaml.

[Copilot]

Pull request overview

This PR improves error handling and messaging when the TypeSpec project directory doesn't exist in a cloned repository at a specified commit. Previously, users would see a confusing raw ENOENT error; now they receive clear guidance about verifying their tsp-location.yaml configuration.

Changes:

• Enhanced error messages in git operations to provide clearer context when git commands fail
• Added validation to check if the TypeSpec project directory exists after cloning and checkout, with a helpful error message directing users to verify their configuration

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
tools/tsp-client/src/git.ts	Wrapped git operation errors with descriptive messages for getRepoRoot, cloneRepo, and checkoutCommit functions
tools/tsp-client/src/commands.ts	Added validation using stat to check if the cloned TypeSpec project directory exists, with a user-friendly error message and cleanup on failure

Comments suppressed due to low confidence (1)

tools/tsp-client/src/commands.ts:398

• The validation added for the main TypeSpec project directory should also be applied to additional directories. After checking out the commit, the code copies additional directories from the cloned repository (lines 393-398), but doesn't verify they exist first. This could result in the same confusing ENOENT error that this PR aims to fix, but for additional directories instead of the main project directory. Consider adding similar existence checks for each additional directory before attempting to copy them.

    for (const dir of tspLocation.additionalDirectories!) {
      Logger.info(`Syncing additional directory: ${dir}`);
      await cp(joinPaths(cloneDir, dir), joinPaths(tempRoot, getAdditionalDirectoryName(dir)), {
        recursive: true,
      });
    }

[catalinaperalta]

/check-enforcer evaluate